Numerical time‐temperature models derived from a 2‐D network of apatite and zircon (U‐Th)/He ages reveal a three‐stage thermotectonic history for the central Arabian rift flank (CARF) of the Red Sea Rift (RSR) system. The pre‐rift Arabian‐Nubian Shield existed as part of a passive Paleo‐Tethyan margin until a widespread tectonic event at ~350 Ma exhumed the proto‐CARF to mid‐to‐upper crustal structural levels. After remaining thermally stable through the Mesozoic, the first phase of RSR extension began with a distinct rift pulse at ~23 Ma when fault blocks across a 150 km wide area were exhumed along a diffuse set of rift‐parallel faults from an average pre‐rift flank depth of 1.7 ± 0.8 km. This rift onset age is mirrored in thermochronometric and sequence stratigraphic analyses elsewhere along the Red Sea Nubian and Arabian margins, confirming that rifting occurred concomitantly along the full Red Sea‐Gulf of Suez rift system. Diffuse lithospheric extension lasted for 8 Myr before a second rift pulse at ~15 Ma, coincident with regional stress realignment, transferred active faulting basinward toward the modern RSR axial trough. CARF time‐temperature models indicate that the prevalent rift style during both RSR extensional phases was one of localized, structurally controlled block faulting and contemporaneous dike injection, not wholesale rift flank uplift.

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Abstract. The Paleocene-Eocene Thermal Maximum (PETM) represents the most pronounced hyperthermal of the Cenozoic era and is hypothesized to have resulted in an intensification of the paleohydrologic cycle, including enhanced seasonality and increased sediment discharge to the coastal ocean. Although the PETM has been widely documented, there are few records from deposits that form the distal, deep-water components of large sediment routing systems. This study presents new constraints on the stratigraphic placement of the PETM in the deep-water Gulf of Mexico basin through analysis of geochemical, carbon-isotopic, and biostratigraphic data within a ~124 m cored interval of the Wilcox Group. Biostratigraphic and carbon-isotopic data indicate that the PETM extends over ~13.4 m based on acmes in the dinoflagellate Apectodinium homomorphum and calcareous nannoplankton Rhomboaster cuspis and a ~−2‰ shift in bulk organic δ13C values. A decrease in bioturbation and benthic foraminifera extinction suggest that deoxygenation of Gulf of Mexico bottom waters was coincident with the onset of the PETM. A ~2 m lag in the depositional record separates the onset of the PETM negative carbon isotope excursion (CIE) and deposition of a 5.7 m thick interval of organic-lean claystone and marlstone that reflects a shut-off of the supply of sand, silt, and terrestrial palynomorphs to the basin. An increase in CaCO3 ~4.5 m above the CIE onset is consistent with other sites that indicate ocean acidification and shoaling of the calcite compensation depth during the early PETM. We interpret deposits of the PETM in the deep-water Gulf of Mexico to reflect the combined effects of increased erosional denudation and rising sea level that resulted in sequestration of sand and silt near the coastline but that allowed delivery of terrigenous mud to the deep-sea. The similarity of oceanographic changes observed in the Gulf of Mexico and Atlantic Ocean during the PETM supports the inference that these water masses were connected during latest Paleocene-earliest Eocene time. Although deposition of typical Wilcox Group facies resumed during and after the PETM recovery, an increased influx of terrestrial detritus (i.e., pollen, spores, organic debris) relative to marine dinoflagellates is suggestive of long-lasting effects of the PETM. This study illustrates the profound and prolonged effects of climatic warming on even the most distal reaches of large (≥1×106 km2) sediment routing systems.

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